1. Field of the Invention
The present invention relates to a printing apparatus and an ink remaining amount detection method thereof and, more particularly, to an inkjet printing apparatus using a mechanism for detecting an amount of remaining ink and an ink remaining amount detection method thereof.
2. Description of the Related Art
Amount of remaining ink detection in an inkjet printing apparatus (to also be referred to as a printing apparatus hereinafter) is done for the purpose of preventing a discharge failure or damage to the printhead caused by a printing operation without ink, or for the purpose of prompting the user to exchange an ink tank. For example, the amount of ink in an ink tank is detected, and the remaining amount is displayed. If the amount of remaining ink is small, the apparatus issues an alarm or stops the printing operation.
Various methods of detecting the amount of remaining ink in an ink tank have been proposed (Japanese Patent Laid-Open No. H6-226989). In some cases, a plurality of amount of remaining ink detection methods are implemented in parallel.
One of the methods of detecting the amount of remaining ink in an ink tank detects the amount of remaining ink using an optical sensor every time the amount of consumed ink, which is calculated from the number of times of ink discharge and the number of times of suction to recover the printhead, reaches a predetermined amount (Japanese Patent Laid-Open No. H8-112910). This is a very accurate amount of remaining ink detection method capable of preventing the detection accuracy from becoming poor because of, for example, variations in the optical sensor itself serving as a detection unit, variations generated by the optical sensor attachment accuracy, and variations in manufacturing ink tanks.
FIG. 1 is a flowchart illustrating an example of a conventional amount of remaining ink remaining amount detection method which is the same as that described in Japanese Patent Laid-Open No. H8-112910.
In step S110, the amount of each ink consumed by ink discharge for a printing operation such as image formation, or preliminary discharge or ink suction executed for a printhead recovery operation is counted as the number of pulses applied for ink discharge. Note that in this prior art, the number of pulses per cycle of suction operation is calculated as 3×106 pulses.
In step S120, it is determined whether the number of pulses counted in step S110 has reached a predetermined number of pulses. In this prior art, the predetermined number of pulses is set to 15×106 pulses. If it is determined that the number of pulses has not reached the predetermined number of pulses, count is continued. If the number of pulses has reached the predetermined number of pulses, the carriage having an ink tank moves to the place of a photo interrupter to measure the light reflectance (output value) of the ink tank in step S130.
In step S140, the amounts of change between output values are calculated based on three output values in the past and that measured in step S130. The sum of the change amounts is obtained. In step S150, the sum of the output change amounts is compared with the sum calculated last time in the same way. It is determined whether the current sum has increased from the preceding sum by a predetermined value α or more.
If it is determined that the current sum has not increased by α or more, the counter for counting the number of pulses is cleared in step S190. The process returns to step S110 to count the number of pulses and acquire the output value again. If it is determined that the current sum has increased by α or more, the process advances to step S160 to display that the ink in the ink tank is running short. In step S170, a process of, for example, interrupting the printing operation and waiting for exchange of the ink tank is executed. The counter for counting the number of pulses is cleared (step S180). As described above, in this amount of remaining ink detection operation, every time a predetermined amount of ink is consumed, output value measurement using the photo interrupter and determination based on the output value are performed. This enables a periodic amount of remaining ink detection operation.
The timing of the amount of remaining ink detection operation is not limited to that described above. For example, when the printing apparatus is powered on, the amount of remaining ink is detected as one of its initialization operations. This operation prepares for an increase or decrease in the amount of remaining ink which is caused due to detachment of an ink tank or printhead, ink refill, or ink evaporation during a period when the printing apparatus is powered off and is incapable of storing a change in the amount of remaining ink. After powering on the printing apparatus, amount of remaining ink detection is executed to confirm the consistency with the amount of remaining ink stored in the printing apparatus.
FIG. 2 is a flowchart illustrating an example of the initialization operation of the printing apparatus after power-on.
In step S240, it is determined whether to turn off or on the hard power of the printing apparatus. If the hard power is already ON, the soft power is turned on (step S250). The process advances to step S320. If the hard power is OFF, the hard power is turned on. In step S260, the soft power is turned on. In step S270, a hard power-on flag is set. The process advances to step S320.
In step S320, in association with printing medium conveyance in the sub-scanning direction with respect to the main scanning direction, that is, printhead scanning direction, an initialization process related to sub-scanning is executed to perform a mechanical operation without any problem and convey a printing medium to a predetermined initial position. In step S330, a lift-up initialization process is executed to vertically move the printhead unit without any problem and locate the printhead at a predetermined initial position. In step S340, a recovery system initialization process is executed to operate, without any problem, a pump, wiper, and cap to be used to clean the printhead and keep it in a good state and place these components at predetermined initial positions. The main body mechanism is initialized in the above-described way in steps S320, S330, and S340. In step S380, the tank is detected to confirm that the ink tank is accurately attached. In step S390, the amount of remaining ink is detected to confirm the amount of remaining ink in the ink tank. In step S400, a suction operation of cleaning the printhead is performed as needed (step S410) based on the elapse time from the last use. In step S420, the printing operation starts.
However, the amount of remaining ink detection operation using an optical unit requires to move the carriage to the position of an amount of remaining ink sensor such as a photo interrupter for light reflectance detection.
Japanese Patent Laid-Open No. H6-226989 described above also shows an arrangement for detecting the amount of remaining ink in an ink tank. However, it is necessary to move the printhead including an ink tank to the position of an amount of remaining ink sensor for amount of remaining ink detection, and the movement takes time. Hence, even when the user wants to print immediately after powering on the printing apparatus, he or she must wait for the end of amount of remaining ink detection operation before the start of printing.